Closes #4163. no review

git-svn-id: http://lampsvn.epfl.ch/svn-repos/scala/scala/trunk@24458 5e8d7ff9-d8ef-0310-90f0-a4852d11357a

src/compiler/scala/tools/nsc/ast/parser/Parsers.scala

@@ -977,7 +977,10 @@ self =>
     def selector(t: Tree): Tree = {
       val point = in.offset
       //assert(t.pos.isDefined, t)
-      Select(t, ident(false)) setPos r2p(t.pos.startOrPoint, point, in.lastOffset)
+      if (t != EmptyTree)
+        Select(t, ident(false)) setPos r2p(t.pos.startOrPoint, point, in.lastOffset)
+      else
+        errorTermTree // has already been reported
     }
 
     /** Path       ::= StableId
@@ -1429,7 +1432,7 @@ self =>
       val t =
         if (isLiteral) atPos(in.offset)(literal(false))
         else in.token match {
-          case XMLSTART => 
+          case XMLSTART =>
             xmlLiteral()
           case IDENTIFIER | BACKQUOTED_IDENT | THIS | SUPER =>
             path(true, false)

test/files/neg/t4163.check

@@ -0,0 +1,7 @@
+t4163.scala:4: error: '<-' expected but '=' found.
+        x = 3
+          ^
+t4163.scala:5: error: illegal start of simple expression
+        y <- 0 to 100
+^
+two errors found

test/files/neg/t4163.scala

@@ -0,0 +1,8 @@
+class Bug {
+  val z = (
+      for {
+        x = 3
+        y <- 0 to 100
+      } yield y
+    ).toArray
+}